1. Field of the Invention
This invention relates to techniques of manufacturing seamless capsules, and more particularly to an apparatus for manufacturing seamless capsules by use of a multiple nozzle.
2. Description of the Prior Art
Among the techniques of manufacturing a capsule having no seam in a shell, i.e. a seamless capsule, there has been known methods wherein a multilayer liquid flow is blown out of a multiple nozzle such as a double nozzle or a triple nozzle to form multilayer liquid drops, and the outermost layer liquid of the multilayer liquid drop is contacted with a hardening liquid to be hardened and thereby sealedly enclose the liquid in the inner layer, this technique being particularly suitable for manufacturing a seamless capsule smaller than a conventional soft capsule although larger than a microcapsule.
In one of these techniques, i.e. in-the-air nozzle method wherein a nozzle disposed in the air is vibrated to produce liquid drops in the air and to drop them into hardening liquid, when the liquid drop impinge on the liquid surface of the hardening liquid, due to the impact of the impingement, the liquid drop is deformed to be flat and may be destroyed in the extreme case. In order to prevent this, the present inventor has previously proposed a method wherein multilayer liquid drops are dropped into the flow of the hardening liquid in the forward direction of the flow (Japanese Patent Laid-Open No. 62-176536).
However, various conditions of manufacturing the capsules are not always constant. For example, in order to manufacture capsules having compositions different from each other, it should be natural that the liquid compositions of the inner and outer layers and the like, and the compositions of the hardening liquids are varied, so that the degrees of deformation are different. Further, even with capsules having the same material compositions, if the particle diameters are different from each other, then the degrees of deformation are different. Furthermore, even if capsules are of the completely identical type, the states of the liquid drops are delicately varied due to the variations in composition among the lots, environmental air temperature, liquid temperature and the like.
As the result, there arise such disadvantages that the seamless capsules having odd-shapes as shown in FIGS. 13(A) through 13(E) are manufactured.
Namely, FIG. 13(A) shows an example wherein a projection 2a is formed on the outer layer B enclosing the inner layer A of a seamless capsule SC. FIG. 13(B) an example wherein the inner layer A and the outer layer B are eccentric from each other. FIG. 13(C) an example where the outer layer B is of an oval shape. FIG. 13(D) an example where wrinkles are made on the outer surface of the outer layer B. and FIG. 13(E) an example where both the inner layer A and the outer layer B are of ellipsoidal shapes, respectively.
In order to always maintain the best conditions according to the changes in the above-described manufacturing conditions, it is conceived to adjust the inclination angle of a U-shaped groove for the flow of hardening liquid in the apparatus disclosed in Japanese Patent Laid-Open No. 62-176586 referred above so that the relative speed between the liquid drops and the flow of the hardening liquid is maintained at optimal.
However, the study of the inventor of the present invention has proved that the above-described method presents the following disadvantages. Namely, (1) it is necessary to change the inclination angle of the nozzle according to the change of the inclination angle of the U-shaped groove while keeping the interval between the nozzle and the U-shaped groove constant, and (2) if the Inclination angle of the U-shaped groove is changed, then the vertical distance and the horizontal distance between the top end and the bottom end of the U-shaped groove are varied, in accordance with which the positions of a hardening liquid tank and a separator should be adjusted, so that adjusting devices become large-sized and complicated, and furthermore, (3) it is difficult to finely adjust the inclination angle of the U-shaped groove, the positions of the hardening liquid tank and separator, and so forth.
Further, the study of the inventor of the present Invention has made it clear that, even with a method wherein a multiple nozzle is provided within the hardening liquid i.e. in-the-liquid nozzle method, the shapes of the liquid drops are delicately changed by the relative speed between the liquid drops and the hardening liquid at a stage where the multilayer liquid drops blown out of the nozzle are hardened. In this "in-the-liquid" case, essentially the measures for adjusting the inclination angle of the U-shaped groove cannot be utilized for a conventional apparatus such as disclosed in Japanese Patent Publication No. 53-1067 because of its structure.